That concession largely emptied the streets of demonstrators in the eastern port city, leaving only small groups of curious onlookers outside the Ningbo government offices, where a large police presence prevented crowds from forming.

At the Zhenhai chemical industrial area, where a foul odor hung in the air, a handful of angry young men manned a makeshift barricade complaining that the local government had never followed through on a 10-year-old promise to pay a subsidy to local residents because of pollution.

“It’s too smelly here,” says a young man wearing a white face mask over his nose and mouth. “We are here to protect people’s rights,” he says, declining to give his name. His complaint is only tangential to the main protest about the paraxylene plant, but it highlights how unhappiness over an environmental issue can easily spark broader grievances about issues like inequality of income.

In the past 15 months, similar protests against large chemical plants have taken place in other big Chinese cities: In the northeastern port of Dalian, an estimated 12,000 people packed the central People’s Square one Sunday in August 2011 to demand that a PX plant located near the coast—and presumably vulnerable in the event of a typhoon grazing the shore—be shuttered and relocated. This summer, hundreds of protesters in the central Chinese city of Shifang demonstrated against the construction of a copper plant, partly due to fears that the earthquake-prone region was an unsuitable location. Earlier this month, residents of a town on the southern island of Hainan, sometimes known as “China’s Hawaii,” protested a proposed coal-fired power plant.

The results of these protests are mixed: Officials in Dalian pledged to shut down the PX plant, but local reports say operations were later resumed. In Shifang, construction on the new copper plant was stopped. In Ningbo, protests continued even after the authorities pledged to halt the PX project, in part because suspicion of the government runs so high. “We don’t trust them at all; we think [their promise] is a stalling tactic,” as one 30-year-old protester in Ningbo wrote in an e-mail to Bloomberg Businessweek on Monday. “We’ll still keep our eyes on them.”

It’s far from a revolution. China’s nascent middle class, the product of the past decade’s economic boom, is looking for better government, not a different one. They’re especially concerned about issues like health, education and property values and often resist the growth-at-all-costs model Beijing has pushed.

The past week’s chemical-plant protests reached an unruly crescendo over the weekend, when thousands of people marched through prosperous Ningbo city, clashing with police at times. The city government gave in Sunday and agreed to halt the plant’s expansion.

Even so, the protesters did not back down, staying outside city government offices hours after the concession. About 200 protesters, many of them retirees, returned Monday to make sure the government keeps its word on the oil and ethylene refinery run by a subsidiary of Sinopec, the state-owned petrochemical giant.

“In yesterday’s protest, the ordinary people let their voices be heard,” a 40-year-old businessman who would give only his surname, Bao, said on the protest line Monday. Government officials, he said, “should say they are completely canceling the project. They should state clearly that they will stop doing these projects in Ningbo and the rest of China.”